Fujitsu 8FX User Manual

MB95630H Series
278 FUJITSU SEMICONDUCTOR LIMITED MN702-00009-2v0-E
CHAPTER 15 8/10-BIT A/D CONVERTER
15.7 Notes on Using 8/10-bit A/D Converter
15.7 Notes on Using 8/10-bit A/D Converter
This section provides notes on using the 8/10-bit A/D converter.
■ Notes on Using 8/10-bit A/D Converter
● Note on setting the 8/10-bit A/D converter with a program
• The contents of the ADDH and ADDL registers are saved at the end of A/D conversion.
Therefore, during A/D conversion, the values resulting from last conversion will be returned
if the two registers are read.
• Do not change the analog input pin select bits (ADC1:ANS[3:0]) while AD conversion
function is being used. During continuous activation in particular, disable continuous
activation (ADC2: EXT = 0) before changing the analog input pin.
• A reset, or the start of the stop mode or watch mode causes the A/D converter to stop and
the ADMV bit to be cleared to "0".
• The CPU cannot return from interrupt processing if the interrupt request flag bit
(ADC1:ADI) is "1" with interrupt requests having been enabled (ADC2:ADIE = 1). Always
clear the ADI bit in the interrupt service routine.
● Note on interrupt requests
If the restart of A/D conversion (ADC1:AD = 1) and the completion of A/D conversion occur
simultaneously, the interrupt request flag bit (ADC1:ADI) is set.
● A/D conversion error
As | Vcc - Vss | decreases, the A/D conversion error increases proportionately.
● 8/10-bit A/D converter analog input sequences
Turn on the analog input (ANn) and the digital power supply (V
CC
) simultaneously, or turn on
the analog input (ANn) after turning on the digital power supply (V
CC
).
Turn off the digital power supply (V
CC
) and the analog input (ANn) simultaneously, or turn off
the digital power supply (V
CC
) after turning off the analog input (ANn).
Ensure that the analog input voltage does not exceed the voltage of the digital power supply
(V
CC
) when turning on or off the power supply of the 8/10-bit A/D converter.
● Conversion time
The conversion speed of A/D conversion function is affected by clock mode, main clock
oscillation frequency and main clock speed switching (gear function).
Example:
Sampling time = CKIN
× (ADC2:TIM[1:0] settings)
Compare time = CKIN
× 10 (fixed value) + MCLK
A/D converter startup time: minimum = MCLK + MCLK
maximum = MCLK + CKIN
Conversion time = A/D converter startup time + sampling time + compare time

Fujitsu 8FX Specifications

General

Brand	Fujitsu
Model	8FX
Category	Computer Hardware
Language	English